Diode Bar Pumping of Single Mode Solid State Lasers

Modern diode laser bars with theirs compact design, energy scaling, by increasing the number of emitters, easy adjustment of the wavelength by temperature, have become basic elements for high-power solid-state laser pumping. A single diode bar is a monolithic linear array which can emit near infrared laser radiation from tens up to few hundreds of watts of power in CW or QCW mode, respectively. However the beam profile of a single diode laser bar is highly asymmetric due to its specific emitting part dimensions and structure (10 000μm) x(~100 μm) including 19-62 diode emitters located on a line with 100-150 μm emitter size and few hundreds μm pitch. In this way, although very good output powers are achieved, the parameters of the laser beam differ vastly in the slow and fast axes. Divergences as well as beam quality factor (M 2 ) in both x and y axes have to be symmetrized in order to obtain efficient single-transverse mode of operation for end-pumped solid-state lasers. Therefore fiber coupled solutions are well spread to symmetrize beam-parameter products in both axes. On the other hand, free space beam-shaping techniques [1] - [2] are more effective in terms of cost, compactness and maximum achievable pump power. However, no easy theoretical procedure has been developed so far to optimize the operation and parameters of the beam-shaping device used for the specific laser bar.